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Electrical Safety and High Energy Physics Dr. Perry L Anthony SLAC Electrical Safety Officer International High Energy Physics Technical Safety Forum 1 4/11/2005 Electrical Hazards in High Energy Physics High Voltage detector components High current power supplies Generally low current, mostly represent a “startle hazard” Possible burns from shorting items across terminals Stored energy Possible burns from shorting, internal damage International High Energy Physics Technical Safety Forum 2 4/11/2005 What determines the hazard? Voltage Current Duration Energy International High Energy Physics Technical Safety Forum 3 4/11/2005 What determines the Damage? I = V R Circuit Path Voltage Resistance Environment Current Waveform Energy Duration Determines Immediate Impact International High Energy Physics Technical Safety Forum P=IxV E=Pxt Damage Done 4 4/11/2005 Injury from R&D Equipment burn injury arc flash electric shock reflex International High Energy Physics Technical Safety Forum 5 4/11/2005 Typical Examples magnet lab generator electroplating supply computer power supply computer circuits CRT monitor photon detector International High Energy Physics Technical Safety Forum 6 4/11/2005 Results of Electric Injury Burn from tool across terminals for a low voltage, high current device International High Energy Physics Technical Safety Forum 7 4/11/2005 Results of Electric Injury (cont.) High Voltage breakdown of skin with entrance/exit wounds International High Energy Physics Technical Safety Forum 8 4/11/2005 Results of Electrical Injury (cont). Arc Flash Burns: International High Energy Physics Technical Safety Forum 9 4/11/2005 Protecting from hazards Engineering controls Keep the hazard isolated Interlocks Administrative Controls Personnel Protective Equipment (PPE) Procedures (application of Lock Out Tag Out) International High Energy Physics Technical Safety Forum 10 4/11/2005 When/What protection is necessary? Codes and Standards specify when/where protection is required: In the US: OSHA NEC NFPA-70E DOE Electrical Safety Handbook Also Facility standards and procedures International High Energy Physics Technical Safety Forum 11 4/11/2005 US: NFPA-70E Standard for Electrical Safety in the Workplace Must protect against both electric shock and possible arc flash Preferred method is to de-energize the equipment Special procedures for testing, troubleshooting, voltage measuring, and similar activities on energized parts Permit with special procedures for other activities on energized parts International High Energy Physics Technical Safety Forum 12 4/11/2005 NFPA-70E: Shock Protection Triggered when working “on or near” exposed energized parts: Over 50V On = tool or body part touching Near = any activity within the “limited approach boundary” (voltage dependent) Requires all body parts within the “Prohibited Approach Boundary” to be insulated against the voltage International High Energy Physics Technical Safety Forum 13 4/11/2005 Limited and Prohibited Approach Boundaries for Electrical Shock Voltage dependent: Prohibited = point where the voltage could jump the air gap Limited = larger region, activity in this region could result in accidental contact Example: 120V: Limited = 42 inches; Prohibited = contact 480V: Limited = 42 inches; Prohibited = 1 inch International High Energy Physics Technical Safety Forum 14 4/11/2005 Arc Flash Protection Boundary Boundary set at point where energy of arc may just cause a 2nd degree burn (blistering) Depends on many factors (e.g. current, duration) May be larger than Limited Approach Boundary for Shock International High Energy Physics Technical Safety Forum 15 4/11/2005 What does that give us? New labels on equipment: Arc Flash hazard labels International High Energy Physics Technical Safety Forum 16 4/11/2005 More arc flash labels International High Energy Physics Technical Safety Forum 17 4/11/2005 Equipment Inspection Labels All electrical equipment must be listed for use by a Nationally Recognized Testing Laboratory (NRTL) or other agency certified by the local Authority Having Jurisdiction (AHJ) International High Energy Physics Technical Safety Forum 18 4/11/2005 Is this enough for the HEP community? NO! Good for shock hazard. Not enough for burn hazards: NFPA-70E and IEEE-1584 give formulas for 60 Hz AC systems only! Nothing about capacitor Banks Nothing about high current low voltage power supplies Nothing about RF systems International High Energy Physics Technical Safety Forum 19 4/11/2005 DOE Electrical Safety Handbook Only 2 out of 11 chapters applicable to HEP: Chapter 9: Enclosed Electrical/Electronic Equipment Chapter 10: Research and Development Gives guidelines for construction Limited guidance for protection International High Energy Physics Technical Safety Forum 20 4/11/2005 Where does that leave the HEP Community? Each facility has needed to develop guidance to ensure worker safety Hazards may not be recognized Standards not uniform International High Energy Physics Technical Safety Forum 21 4/11/2005 Six US Facilities International High Energy Physics Technical Safety Forum 22 4/11/2005 Where do we go from here? Capitalize on the expertise in the HEP community to develop standards for situations and equipment not covered by existing codes (e.g. RF, capacitor banks) Use forums like this one to work towards uniform standards International High Energy Physics Technical Safety Forum 23 4/11/2005 Initial steps The DOE Electrical Safety Handbook is a step in this direction. Efforts are underway to establish an international committee under ISA to develop standards for High Energy R&D Electrical Systems. International High Energy Physics Technical Safety Forum 24 4/11/2005 High-Power Research and Development Electrical Systems Standards Committee Scope To develop standards, recommended practices, technical reports and related information documenting design, fabrication, installation, operation, and maintenance of high power electrical systems, and their associated control, monitoring, safety, and protection systems for national and international research programs in accelerators, pulsed power applications, and high power lasers. - From the 2005 R&D Electrical Safety Meeting and Workshop held at SLAC March 28-31 International High Energy Physics Technical Safety Forum 25 4/11/2005